While creeping through a dinosaur-era forest, two spiders found themselves enveloped in a pool of tree resin. Now, after millions of years of entombment, the well-preserved pair have been identified as members of a new arachnid species.
Thought to be around 99 million years old, the ancient spiders have incredibly long projections extending from their upper shells, or carapaces, as well as complex, horned fangs.
The now extinct spider, found in a chunk of amber, was added to the Tetrablemmidae family, which includes an array of tiny, heavily armored spiders that live in tropical or subtropical regions, primarily in the Southern Hemisphere.
The researchers dubbed the ancient species Electroblemma bifida—the name in part refers to a unique doubly split tip at the end of its carapace projection.
“This is a particularly bizarre form of this armored spider family,” says Paul Selden, an invertebrate paleontologist at the University of Kansas, whose team described the new species in a paper published online in June in the journal Cretaceous Research.
Though the carapace projection is relatively common among living members of this spider family, says Selden, the size of the feature on the Cretaceous species is extreme even by modern-day standards.
Because the projection expands at the end and has four corners, Selden believes it would have held the spider’s eyes, though they were not visible in the fossil specimens.
Erin Saupe, a paleobiologist at Yale who was not involved with the study, agrees with that assessment, adding that a modern member of the Tetrablemmidae family has its eyes positioned on a similar projection.
As for the horned fangs, Selden believes they are a sexual characteristic that enables males and females of the species to recognize each other. Though other males in this family also have horned fangs, the new species has unique prongs at the tips. The fangs could also be used for protection or hunting.
The newly discovered specimens are entombed in Burmese amber, which originates in the Hukawng Valley of northern Myanmar.
This amber has been used for over 2,000 years for carvings and other art, says Ryan McKellar, the curator of invertebrate paleontology at the Royal Saskatchewan Museum. Over the past 20 years, mines in the Hukawng Valley have become the most productive sources of Cretaceous insect and arachnid fossils, generating nearly 10 tons of material to date.
Selden acquired the new spider specimens through his study co-author Weiwei Zhang, a collector of Burmese amber. The specimens are currently housed at Capital Normal University in Beijing but will eventually be deposited in the Three Gorges Entomological Museum in Chongqing, China.
Taken as a whole, fossils found in Burmese amber provide a snapshot of the biodiversity, vegetation, and climate during the late Cretaceous.
“Fossils are windows to the past and provide a way to understand the timing and mode of diversification of life on Earth,” Saupe says in an email. “By studying fossils, we can get an idea of where certain groups first originated and how they diversified through time.”
For instance, scientists know that the armored spiders alive today are protecting themselves against spider-hunting wasps, explains Selden. If such wasps are also found in Burmese amber, he continues, it would reveal similar predator-prey dynamics from a hundred million years ago.